Steel for permanent magnets



Patented Jan. 18, 1938 UNITED STATES PATENT OFFICE No Drawing. Original application November 13,

1933, Serial No. 697,874. Divided and this application July 18, 1934, Serial No. 735,898.

Japan May 1, 1933 4 Claims.

This invention relates to improvements in alloys for permanent magnets and more particularly to an alloy consisting mainly of nickel, titanium, cobalt and iron, and has for its object 5 to provide a permanent magnet which has a very high coercive force and long durability. This forms a division from copending application 'Ser. No. 697,874, filed November 13, 1933.

Heretofore commonly used magnet steels such as tungsten steel, chrome steel and the like have comparatively small coercive force of only 60 to 70 gausses and if such alloy steels are used as a permanent magnet they lack durability and are especially unsuitable for a magnet of smaller di- 5 mension-ratio, that is, having a small ratio of the length and diameter. Moreover, such alloy steels are greatly affected by temperature variations and mechanical shocks and show unstable magnetic properties.

m This invention is to obviate the above mentioned detects and to provide an alloy which is well adapted for a permanent magnet of a smaller dimension-ratio, and possesses stable magnetic properties for temperature changes and mechanias gal shocks and has particularly high coercive orce.

The alloy of this invention can be obtained by melting together nickel, titanium, cobalt and iron in the proportion of 3 to 50% nickel, 8.1 to 50% I) titanium, less than 60% cobalt and the remainder iron. The preferred composition of the alloy may be of 10.1 to 40% nickel, 8.1 to 40% titanium, less than 50% cobalt and the remainder iron. The molten product may be cast in a suitable mold or 35 sucked up into a tube of refractory material to give a desired shape. The cast product is preferably annealed at a. suitable temperature such as 500 to 800 C. to give it stability.

As above described, though the alloy of this in- 40 vention may be obtained by melting together iron,

nickel, cobalt and titanium at a proper proportion, yet it is more convenient in practice to use iron or mild steel, nickel, cobalt and ferro-titanium.

As for example, the following alloy of this invention shows magnetic properties as follows:-

Iron Remainder Residual magnetic in- Such magnetic properties are obtained by casting the alloys and afterwards annealing them at about 670 C. for two hours. It will be recognized that the above alloys show particularly high coercive force.

The alloys of the present invention may also contain any one or more of copper, molybdenum, aluminium, arsenic, vanadium and manganese in the proportion of less than 20% each for a further increase of the residual magnetic induction and the coercive force.

Accordingly the alloy of this invention is well adapted for the material of permanent magnets in general and more especially of smaller dimension-ratio and it has very-stable structure at a temperature below about 700 C. and its magnetic properties are not substantially affected by the change of temperatures and thus it is most suitable for the material of permanent magnets for fine instruments and also for heat resisting permanent magnets.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An alloy containing about 16% of nickel, 11% of titanium, 28% of cobalt and the remainder iron, characterized by a. coercive force of about 830 gausses.-

2. A permanent magnet formed of an alloy containing 3 to 50% of nickel, 8.1 to 50% of titanium, cobalt to the extent of not over 60% and at least 20% iron and a small amount of impurities, characterized by a coercive force in the neighborhood of 250 gausses or more.

3. A permanent magnet formed of an alloy containing 10.1 to 40% of nickel, 8.1 to 40% of titanium, .01 to 50% of cobalt and at least 20% iron and a small amount of impurities, characterized by a coercive force in the neighborhood 01' 250 Eausses or more.

4. For permanent magnets an alloy containing about 16% of nickel, 11% of titanium, 20% of cobalt and the remainder iron, characterized by a coercive force 01' about 830 gausses.

KOTARO HONDA. 

